Guard your sanity in the waiting room of life

Elmgreen and Dragset: The Welfare Show Serpentine Gallery, London W2 until 26 February

I met her in the ladies', shivering like a winter sparrow. She was trying to warm her hands beneath the drier. Despite the uniform, she didn't look like a real gallery guard - too excitable, too badly nourished - and it turned out that she wasn't. Next time I saw her, she was part of the art.

Ten guards in black clothes confront you round a sudden corner at the Serpentine. Meeting your eyes, their stare is a shock. Where to look? How to escape their scrutiny, or the embarrassment of treating them as exhibits? The social anxiety becomes overwhelming. Visitors hesitate, and then hurry onwards.

These guards who guard nothing, these people sitting it out on their hard plastic chairs, watching and waiting as instructed - they must be recruits from a job centre. But this thought only occurs later, along with the sense that this might be the perfect parody of a social system that requires the able-bodied to take any job going, no matter how menial or pointless, to reduce the unemployment figures. For here they are, these people, these unemployed figures, temporarily hired quite literally as bodies.

I tried to talk to my guard, to break the spell, but she managed not to notice. How cold was she? How much was she getting paid? And what about the guard in the wheelchair presiding over the first room, which contains nothing but an empty wheelchair - was he actually disabled? Does the Serpentine make a point of equal opportunities? Michael Elmgreen (born Denmark 1961) and Ingar Dragset (born Norway 1969) love to raise such awkward questions with their work.

For The Welfare Show they have transformed the gallery so skilfully into a maze of corridors, waiting areas and anonymous spaces that not a trace of high-art ozone remains. The atmosphere is that of a sick building, all tension, strip lighting and white noise. Each mise en scene evokes some painful experience common to us all; and each leads, as seamlessly as in a dream, to another that may be more disturbing.

Escape those guards, for instance, and you enter a baggage hall where a solitary holdall trundles round the carousel, ominously unclaimed, as if the owner was lost in transit. Or stateless, like those refugees who can never get beyond the airport, transported, deported, shuttled back and forth forever between nations. And sure enough there is no way out: try to leave and the staircase that leads to the exit has crumbled away.

Sink into a nearby seat and you are faced with an implacably closed door, a pot plant and a ticket dispenser that numbers your place in the queue. Immediately your mind turns to doctors, lawyers, long-awaited appointments. Not that your slot will ever come up, for the electronic sign just keeps flashing up a row of zeros. This is not one but two cliches - from reality and dream - yet it irresistibly produces a sense of anticipation and dread.

Elmgreen and Dragset make a theatre of art gallery space. Their installations function like stage sets on which the audience, wandering in, involuntarily become the performers. In New York they constructed a subway station in a basement gallery. You descended, found yourself on the platform and could hardly help wondering what happened to the train. Some visitors even claimed to miss the vermin and litter.

The longer you stay on the platform, or in the waiting room, searching for clues to the particular situation, the more you are in effect waiting. You make the fiction a reality. Besides which, Elmgreen and Dragset tend to avoid the particular. Not for them the dense local detail you get with other artists who construct walk-in scenarios - from Ed Kienholz to Ilya and Emilia Kabakov or Gregor Schneider. The Scandinavian duo could almost be described as minimalists. Aside from their notorious 'Prada' shop in Marfa, Texas - a parodic fascimile of a fashion outlet in the middle of the desert - their installations are faultlessly neutral.

So the cash machine by which a baby has been abandoned displays no brand. The wheelchair to which a balloon has been tethered bears no trademark, or traces of an owner. A mop and bucket beside a pole-dancing stage could be any nightclub after hours: the connection between the two types of labour is universal.

Obviously the danger with this show is that it becomes too literal, partakes too much of the cliches that are its subject. Certainly the row of locked doors is hardly Kafka. But oddly enough it is form and not content that lets things down. At one point you must squeeze past two hospital trolleys in a corridor. One is empty, the other contains a patient - or would, in one's horrified mind, except that this neglected person (like the baby) is so clearly a waxwork.

And then again, this is not evident until you have come right up close to the face. By which time the idea of patients dying as people pass by without noticing has entered the mind and will likely stay there - along with thoughts of poverty, wage slavery, unemployment, asylum, the ruination of the health services, one's own fear of hospitalisation, abandonment, death.

At its most fundamental, this art is all about consciousness-raising. Yet it plays its hand so much more lightly than that suggests. Sure enough, the wheelchair seems to make such a heavy point about treating the disabled as if they were children, but the balloon lifts high and free. The cash machine is on the blink. The pot plant is wilting. The ticket dispenser has run out of tickets because so many people have tugged at it. And as for the fake guards, how marvellously their humanity undermines the pervasive unease: they yawn, suppress a smile and stretch.